Microstructure Control for Improving Swelling Behavior of Lithium Ion Batteries

Abstract

With the growing demands for high energy density of lithium ion batteries (LIBs), the electrode is thicker and denser to maximize the proportion of the active materials compared to the electrochemically inactive components such as current collectors and a separator. Accordingly, the electrode could lose the interconnection between pores and have reduced pore volume in the electrode, resulting in poor electrochemical properties due to the degradation of electrolyte permeability. Furthermore, the inhomogeneous volume changes of active materials in the electrode could cause the severe swelling issues in the thick and dense electrode system. Here, we report the thick and dense graphite anodes with the controlled pore distribution in the electrode to improve the electrochemical properties and secure the stable electrode swelling behaviors by two-step roll pressing. The uniform pore distribution in the electrode is confirmed by 3D X-ray microscopy (3D XRM). The graphite anode with the uniform pore distribution exhibits improved cycling performance (retention 85.83% @200cycle), and presents stable swelling behavior (4.47% @25cycles). We demonstrate that the improved electrochemical properties and stable swelling behaviors are realized in the thick and dense graphite anodes by facile two-step roll pressing.